Incorrect.
Both are feasible and achieve the same objective value, so they are
equally good.

False.

Correct!

Design D cannot be optimal.

True.

Correct!

False.

Incorrect.
Design A is also feasible and achieves a better objective value
(lower power consumption).

Very roughly, how long would it take to solve a linear program with 100
variables and 1000 constraints on a computer capable of carrying out a billion
floating point operations per second (1 gigaflop)?

Microseconds.

Incorrect.

Milliseconds.

Correct!

Seconds.

Incorrect.

Minutes.

Incorrect.

Local optimization

can be quite useful in some contexts, and therefore is widely used.

Correct!

is currently illegal in 17 states.

Incorrect.

can't guarantee finding a (global) solution, and so is not widely used.

Incorrect.
Though they can't guarantee finding a global solution, they are nevertheless
useful and widely used.